The heart of a computer is a magnetic hard disk drive (HDD) which typically includes a rotating magnetic disk, a slider with read and write heads, a suspension arm above the rotating disk and an actuator arm that swings the suspension arm to place the read and/or write heads over selected circular tracks on the rotating disk. The suspension arm biases the slider into contact with the surface of the disk when the disk is not rotating but, when the disk rotates, air is swirled by the rotating disk adjacent an air bearing surface (ABS) of the slider causing the slider to ride on an air bearing a slight distance from the surface of the rotating disk. When the slider rides on the air bearing the write and read heads are employed for writing magnetic impressions to and reading magnetic signal fields from the rotating disk. The read and write heads are connected to processing circuitry that operates according to a computer program to implement the writing and reading functions.
The volume of information processing in the information age is increasing rapidly. In particular, it is desired that HDDs be able to store more information in their limited area and volume. A technical approach to this desire is to increase the capacity by increasing the recording density of the HDD. To achieve higher recording density, further miniaturization of recording bits is effective, which in turn typically requires the design of smaller and smaller components.
However, the further miniaturization of the various components, particularly, the size and/or pitch of magnetic grains, presents its own set of challenges and obstacles in conventional HDD products. Noise performance and spatial resolution are key parameters in magnetic recording media and are ongoing challenges to advance the achievable areal density of media. The dominant media noise source today is transition jitter. In sputtered media, it reflects the finite size, random positioning and dispersions in size, orientation and magnetic properties of the fine grains that comprise the media.
In order to address grain size and transition jitter it was proposed to change the recording mechanism from conventional magnetic field recording to heat assisted magnetic recording (HAMR), also known as “thermally assisted magnetic recording” TAR or TAMR. HAMR recording employs heat to lower the effective coercivity of a localized region on the magnetic media surface and write data within this heated region. The data state becomes stored, or “fixed,” upon cooling the media to ambient temperatures. HAMR techniques can be applied to longitudinal and/or perpendicular recording systems, although the highest density state of the art storage systems are more likely to be perpendicular recording systems. Heating of the media surface has been accomplished by a number of techniques such as focused laser beams or near field optical sources.
Thermal management is an important factor in HAMR recording. For example, high operating temperatures can lead to serious damage to HAMR heads. Moreover, while the magnetic media needs to be heated to high temperatures (e.g. at least 100K above Tc) during the writing process, the media also needs to be cooled quickly in order to avoid thermal destabilization of the written information. However, faster cooling rates may require more heating power to achieve the desired temperatures.
Conventional heat sink layers are thus typically used in HAMR media to conduct or direct heat away from the recording layer after writing in order to limit thermal erasure. However, conventional heat sink layers may conduct heat both vertically and laterally, thereby resulting in possible lateral thermal spreading during the writing process, which may limit track density and the size of the data bits. Moreover, conventional metallic materials with high thermal conductivity such as pure Cu, Ag, Al, etc. are often too soft and mobile, and therefore do not possess sufficient mechanical durability or a surface roughness acceptable for HDD technology.
A need therefore exists for magnetic media that can be used in heat assisted magnetic recording systems that provide a suitable thermal design for heat confinement and management in the media.